3,295 research outputs found

    USE OF PLASTIC DRIFT CARDS AS INDICATORS OF POSSIBLE DISPERSAL OF PROPAGULES OF THE MANGROVE AVICENNIA MARINA BY OCEAN CURRENTS

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    Plastic drift cards with the same buoyancy as propagules of Avicennia marina (Forssk.) Vierh. were used as an indicator of possible mangrove dispersal by ocean currents. The cards were dropped from an aircraft into the sea at the mouths of the Mhlathuze River off Richards Bay, the Mgeni River off Durban and the Nxaxo-Ngqusi rivers off Wavecrest on the east coast of South Africa. Details of the time and locality of strandings were recorded from cards returned. Of the 4 500 cards released, 133 (8.9&#37), 146 (9.7&#37) and 280 (18.7&#37) were returned respectively from the above locations. The high returns from Wavecrest were attributable to cards being washed ashore in the immediate vicinity of the dropping point. A high percentage of the cards dropped at Durban were transported northwards by the inshore counter-current. Approximately 68 and 32&#37 of the cards recovered for Richards Bay and Durban respectively were transported by the Agulhas Current and were stranded farther south along the East and South-East coasts. Cards that reached the Agulhas mixing area were deposited ashore on the Cape Peninsula and the West Coast (3&#37), or were transported either across the Atlantic Ocean to South America or the Indian Ocean to Australasia (4&#37). Estimated transport rates of cards to South America and Australasia were similar to previously published values. The results indicate that the northern estuaries could provide propagative material over a considerable portion of the South African coast, which could result in a wider distribution of mangroves in the Eastern Cape.Afr. J. mar. Sci. 25: 169–17

    Absolute calibration of GafChromic film for very high flux laser driven ion beams.

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    We report on the calibration of GafChromic HD-v2 radiochromic film in the extremely high dose regime up to 100 kGy together with very high dose rates up to 7 × 1011 Gy/s. The absolute calibration was done with nanosecond ion bunches at the Neutralized Drift Compression Experiment II particle accelerator at Lawrence Berkeley National Laboratory (LBNL) and covers a broad dose dynamic range over three orders of magnitude. We then applied the resulting calibration curve to calibrate a laser driven ion experiment performed on the BELLA petawatt laser facility at LBNL. Here, we reconstructed the spatial and energy resolved distributions of the laser-accelerated proton beams. The resulting proton distribution is in fair agreement with the spectrum that was measured with a Thomson spectrometer in combination with a microchannel plate detector

    Dynamics of Nanometer-Scale Foil Targets Irradiated with Relativistically Intense Laser Pulses

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    In this letter we report on an experimental study of high harmonic radiation generated in nanometer-scale foil targets irradiated under normal incidence. The experiments constitute the first unambiguous observation of odd-numbered relativistic harmonics generated by the v×B\vec{v}\times\vec{B} component of the Lorentz force verifying a long predicted property of solid target harmonics. Simultaneously the observed harmonic spectra allow in-situ extraction of the target density in an experimental scenario which is of utmost interest for applications such as ion acceleration by the radiation pressure of an ultraintense laser.Comment: 5 pages, 4 figure

    Development of a decision support tool to facilitate primary care management of patients with abnormal liver function tests without clinically apparent liver disease [HTA03/38/02]. Abnormal Liver Function Investigations Evaluation (ALFIE)

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    Liver function tests (LFTs) are routinely performed in primary care, and are often the gateway to further invasive and/or expensive investigations. Little is known of the consequences in people with an initial abnormal liver function (ALF) test in primary care and with no obvious liver disease. Further investigations may be dangerous for the patient and expensive for Health Services. The aims of this study are to determine the natural history of abnormalities in LFTs before overt liver disease presents in the population and identify those who require minimal further investigations with the potential for reduction in NHS costs

    Efficient ion acceleration by collective laser-driven electron dynamics with ultra-thin foil targets

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    Experiments on ion acceleration by irradiation of ultra-thin diamond-like carbon (DLC) foils, with thicknesses well below the skin depth, irradiated with laser pulses of ultra-high contrast and linear polarization, are presented. A maximum energy of 13MeV for protons and 71MeV for carbon ions is observed with a conversion efficiency of > 10%. Two-dimensional particle-in-cell (PIC) simulations reveal that the increase in ion energies can be attributed to a dominantly collective rather than thermal motion of the foil electrons, when the target becomes transparent for the incident laser pulse
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